In the manufacture of current-producing electrochemical cells, such as secondary battery cells, a membrane separator is often needed between electrode compartments. The membrane separator is required to selectively pass ions from one compartment to the other. These ion-exchange membranes are usually quite expensive, and can be the limiting factor in the cost of production.
Microporous membranes having no ion selectivity have not been successfully substituted for the more expensive ion-selective membranes. Such substitutions generally result in drastic reductions in coulombic efficiencies and are unacceptable from the standpoint of cell performance.
The invention seeks to provide a method of improving the ion selectivity of membranes, wherein a low-cost electrochemical cell with acceptable coulombic efficiences can be fabricated.
The invention proposes to utilize low-cost, non-selective microporous membranes as battery separators by increasing in situ their capability to pass only select ions, and to furthermore achieve this capability in a low-cost manner.